1. Field of the Invention
The present invention relates to an image pickup, device, and, in particular, to a solid-state image pickup device of the type which comprises image pickup or photosensitive cells arranged in a one-dimensional or two-dimensional array and which produces a current associated with generated photocarriers, and a method of manufacturing the solid-state image pickup device.
2. Description of the Prior Art
A two-dimensional solid-state image pickup device comprising a photosensitive cell array has been well known in which photosensitive cells such as photodiodes are arranged to form a two-dimensional array having horizontal lines and vertical columns. Along at least one of the horizontal lines and vertical columns, the photosensitive cells involved are sequentially selected by a shift register to produce pixel signals therefrom. Such devices in which shift registers are utilized for accessing cells in the horizontal and vertical directions are collectively called an MOS-type image pickup device. Specifically, a device in which a shift register is used in association with the vertical direction so as to transfer electric charge in the horizontal direction is referred to as a charge priming device (CPD).
When reading out a pixel signal in the raster scanning fashion from a two-dimensional image pickup device including shift registers for selecting a photosensitive cell in a two-dimensional array, the direction for reading out the cells is uniquely defined for the device depending on the shift register specified for accessing the photosensitive cells.
This restriction causes the following problem in a camera comprising a couple of solid-state image pickup devices.
A camera having such twins of image pickup devices has an advantage that a higher resolution can be developed when compared with a camera utilizing a single image pickup device, moreover, it does not have a drawback that a faulty color signal appears on an edge of an image of an object having a great difference in luminance due to the special color separation, which takes place when a single image pickup device is used.
In the past, however, since the direction for reading pixel signals in a two-dimensional image pickup device was uniquely fixed to the device, identical, orthoscopic images of an object must be formed on the image pickup arrays of two image pickup devices. For this purpose, a prism in which total reflection is developed has been adopted to obtain the orthoscopic image.
The prism, however, has a drawback that it is complex in its shape and has a heavy weight. To eliminate such a prism, it has been considered that a mirror image of an object is established in two image pickup devices by use of a beam splitter, and that thereafter these mirror images are converted into video signals representative of two orthoscopic images of the object in a certain method. In this case, for example, a buffer is required to store the pixel signals developed from the two image pickup devices for each horizontal scanning line and to read out the stored signals in the reversed sequence to the signal storing sequence. Alternatively, it must be devised that the pixel signals obtained from two image pickup devices are stored on a magnetic recording medium without any modification to be conducted on the signals, and that the recorded signals originating from one of the two image pickup devices are read out from the recording medium in the reverse direction to the storing direction.
Such means for inverting images may, however, be dispensed with, if an image pickup device is available from which picture element signals indicative of an orthoscopic image are produced when a mirror image of an object is formed on the photosensitive array thereof. It is therefore required to utilize a two-dimensional image pickup device which allows the video signals of an orthoscopic image to be produced on the basis of the mirror image information stored in such image pickup cells. However, such an image pickup device for inversely reading mirror image information is required to include read shift registers for such read operations which are wired in electric connection specific to the read operation.
In more detail, in order to appropriately read out mirror image signals in the reverse direction, it is required to enable either one of the vertical and horizontal shift registers in its reverse direction, which is opposite to the direction in which signals of an orthoscopic image is produced. In the device for inversely reading out mirror image signals, the electrical wiring connecting the respective stages of the shift register is also reversed to that involved in a device for reading out an orthoscopic image, with an initiator and a terminator connected with the first and last stages thereof, respectively, exchanged in position as compared with normal devices. Consequently, the solid-state image pickup device for reading out inversed mirror image information has to be manufactured by using a mask of a circuit pattern dedicated to the reverse read operation.
That is, in order to manufacture above-stated image pickup device, a special mask pattern other than that for a solid-state image pickup device for reading out orthoscopic image signals is required in separate manufacturing processes. Since the demand for such an image pickup device is less than that for the image pickup device for reading out orthoscopic image signals, the special pattern and dedicated manufacturing process cause the device price to soar and to complicate the management for manufacturing such devices.